As bee populations decline all over the world, researchers in Switzerland have found another clue as to the cause: a common insecticide may act as a bee contraceptive.

The study, from the University of Bern, looks at the effect of two neonicotinoids, the nicotine-like insecticides used on industrial crops and which are already known to affect female bees. They found these chemicals reduce bee sperm quantity by 39% and also shorten the life-span of drones.

To make these findings the team took drone honeybees from colonies that had been exposed to neonicotinoid insecticides and kept them in the lab until they had reached sexual maturity. Compared to a control group, they found the drones–the male bee whose primary role is to mate with the queen–suffered a major reduction in both sperm quantity and quality.

“We know multiple stressors can affect honeybee health, including parasites and poor nutrition,” senior author Geoff Williams said in a press release. “It is possible that agricultural chemicals may also play an important role.”

The study was started after Switzerland and the European Union restricted the use of common neonicotinoid insecticides in order to assess their risk.

Day to day, there’s not much you or I can do about this industrial decimation, but we can help out in our own way. If you live in the city, for instance, then make sure to keep some bee-friendly plants growing on your window ledges or balconies, so the furry little fellas can at least get around town without starving.

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